the 18th century, the Jesuit missionary activity had increased as they were trying to convert Encabellados into Catholicism and unite them into reductions. The reductions turned out to be unsuccessful, and eventually, the Jesuits were expelled from the Americas. Siona people refer to themselves as bai, meaning "people" and refer to their language as baicoca which means "the language of the people." The limited contact between the Siona and the Spanish-speaking world did not last very long and was drastically increased after the rubber boom in the late 19th century. In 1955, a missionary couple, Maria and Orville Johnson of the Summer Institute of Linguistics arrived in Sucumbíos. This led to more contact between the Spanish and the Siona. The Johnsons developed a writing system for Siona based on Spanish orthography, which is to this day used by the Siona people of Ecuador. After the oil companies arrived in 1967, the contact reached a critical state. External factors, such as missionary activity, international tourism, and the presence of the oil industry, have contributed to the decline of native Siona speakers. Some internal factors also play a role, such as changes in the intermarriage patterns and migration. The traditions behind intermarriage used to involve unions between the Siona, the Secoya, and Cofán indigenous groups, making the three more culturally united. Siona and Secoya can be after all considered varieties of the same language. However, their intermarriage practices have extended to other groups probably because the three groups are very small. Today, the Ecuadorian Siona marry other indigenous groups, such as the Amazonian Kichwa and the Shuar, whose languages are unrelated to Siona. They also marry mestizos, that is non-indigenous people of Ecuador. As a result, many Ecuadorian Siona children grow up speaking one language – Spanish. Phonology The phonemic inventory in Ecuadorian Siona is large relative to other Tukanoan languages, consisting of 17 consonantal phonemes and 12 vocalic phonemes. For the proto-Tukanoan language, only 9 consonants and 12 vowels have been proposed. (C)V(V)(H) represents the basic syllable structure in Ecuadorian Siona, where H stands for the glottal stop [ʔ] or the glottal fricative [h]. Long vowels and diphthongs are generally restricted to open syllables, while closed syllables contain short vowels. Only the glottal consonants appear in the coda position, and words generally do not end with closed syllables, except for borrowings, such as the Spanish loanword [mõh.tor] ‘motor’. Consonants The Siona's